American voters will deliver a verdict on the first two years of President Donald Trump's second term in Tuesday's midterm elections, with polls and nonpartisan analysts favoring Democrats to wrest the House from Republicans while control of the Senate remains uncertain. The battle for the Senate is unfolding across nearly 10 closely ​contested statewide races, most in Republican strongholds. History is against Trump's Republicans: the sitting president's party has lost ground in Congress in all but two midterm elections since World War Two. Trump's approval rating is hovering ‌near his all-time lows, dragged down by deep voter frustration over the war with Iran and the resulting rise in fuel prices. There is little doubt this year's election is all about Trump, the central US political figure for most of the last decade. Trump himself has told his supporters repeatedly to "pretend I'm on the ballot," a message Democratic leaders have happily echoed. The president has held more than two dozen campaign rallies since the start of October, the vast majority in states he easily won in 2024, underscoring the extent to which Republicans are playing defence. Read: Candidates make final push for US midterms Led ​by Trump, Republicans have portrayed Democratic candidates as radical, un-American and even communist. "The Democrat Party has nominated the most extreme and dangerous slate of candidates in American history," Trump said on Monday during a speech in Washington. But opinion ​polls show voters are most concerned about affordability and disapprove of Trump's handling of the issue, after his sweeping tariff policy and his decision to attack Iran in February increased domestic ⁠costs. Republican candidates, meanwhile, have struggled to distance themselves from a president who demands fealty and rarely acknowledges mistakes. All 435 seats in the US House of Representatives are up for election, along with 35 of the Senate's 100 seats, though the majority ​of contests are not considered competitive. Democrats must flip at least three House seats and four Senate seats to win a majority in each chamber. A Democratic House or Senate could launch investigations into what Democrats describe as self-dealing by the Trump administration and ​demand concessions to approve legislation. A Democratic Senate would also have the power to block Trump appointments, including US Supreme Court nominations if vacancies arise. But while Democrats have put Republicans on the defensive on much of their home turf, they have little margin for error. The party must defend all of its current seats, including a tight race in Michigan, while winning at least two states that voted for Trump by a double-digit margin two years ago: Alaska, Iowa, Kansas, Nebraska, Ohio, South Carolina and Texas. Opinion polls show Democrats either narrowly leading or within striking distance in all of ​those states. Michigan race roiled by cross-party endorsement The Michigan Senate contest between progressive Democrat Abdul El-Sayed, 42, and Republican former US Representative Mike Rogers, 63, received a fresh jolt on Sunday, when Democrat Haley Stevens, who narrowly lost to El-Sayed in the party's primary ​election, endorsed Rogers in a surprise reversal. In addition to the implications for Senate control, the Michigan race represents a high-profile test of whether Republicans' identity-based attacks – El-Sayed would be the nation's first Muslim senator — prove effective in a battleground state. A win for El-Sayed, who has criticised Israel and supports liberal policies such as universal healthcare, would also boost the party's left wing ahead of the 2028 presidential election. Read more: Israel maintains highest state of alert on eve of US midterm elections The Alaska Senate race has been caught up in its own turmoil, after the New York Times reported that the campaign of Democratic candidate Mary Peltola, 53, helped recruit a third candidate who shares the first and last name of her Republican opponent, Dan Sullivan, 61. Peltola has denied involvement. Trump's Justice Department has launched a criminal probe into the allegations and filed a lawsuit to block certification of the election results, though a judge dismissed the latter effort. In Texas, Democratic Senate candidate James Talarico, 37, has his party once again dreaming of winning the biggest Republican state after decades of heartbreak. His scandal-plagued opponent, Republican Attorney General Ken Paxton, 63, has benefited ​from a nine-figure investment from the world's richest man, Elon ​Musk, who has spent hundreds of millions of dollars boosting ⁠Republicans. In Kansas, Democrat Adam Hamilton, 62, a megachurch pastor, held a narrow polling lead over Republican US Senator Roger Marshall, 66. The state voted for Trump by more than 16 percentage points in 2024 and has not elected a Democratic senator in nearly a century. And in Maine, Republican US Senator Susan Collins, 73, is once again seeking to defy the Democratic leanings of her home state ​and win a sixth term. She faces Democrat Troy Jackson, 58, a former state senate president who unexpectedly became the nominee after Democratic oyster farmer Graham Platner dropped out amid ​accusations of misconduct, which he denied. Other ⁠competitive Senate races are taking place in Iowa, Nebraska, Ohio and South Carolina, all Republican-held seats. Trump's Justice Department intervenes There are 47 US House races widely seen as competitive, according to a Reuters analysis of the leading election forecasters. If the other contests all proceed as predicted, Democrats would need to win only 13 of those 46 races to secure a majority. The fight for the House has been waged largely on Republican turf, including some districts Trump carried by double digits in 2024. A Trump-backed Republican effort to redraw districts in several states ⁠to make them ​safer for the party appears not to have yielded the gains the White House expected. Democrats have warned that Trump, who has long falsely claimed that US elections ​are rigged, may attempt to challenge Tuesday's results if Republicans lose. In addition to its actions in Alaska, Trump's Justice Department also filed a lawsuit in California to block ballots it says may be invalid, a break from decades of practice meant to insulate elections from political influence. The US Supreme Court on Monday rejected the ​administration's request for an emergency order in the case. Three dozen governors' races will also take place on Tuesday, as well as thousands of state-level legislative contests and ballot measures on everything from a billionaires' tax to abortion rights. Economic discontent Republicans insist that Trump's tax cuts and immigration crackdown will benefit Americans, and they are portraying Democratic candidates as left-wing radicals. But in his final public campaign appearance Monday, Trump barely touched on the economy and spent most of the time in a rambling talk about his problem-plagued renovation of Washington's Reflecting Pool. "This is the last day before the midterm elections, the most important midterm I believe in our lifetime," he said, 26 minutes into the speech, before quickly returning to talking about renovations. Senate Democratic leader Chuck Schumer branded it a "pathetic closing message." Some Republican supporters remain confident. Also read: US midterms: Polls show Democrats ahead in battle for Congress "We're going to win. As a matter of fact, we've probably already won," Texas military veteran Yvonne Clouser told AFP. But while Republicans hold a 53-47 Senate majority, the battlefield is extending into conservative states like Kansas, Texas, Iowa, Ohio and Alaska. Decision Desk HQ's final forecast projected 241 House seats for Democrats against 194 for Republicans, and a narrower 52-48 Democratic Senate majority. Disputed results? Polls can underestimate one party's support, and Republicans hope their voters turn out in force on Election Day. More than 57 million Americans had already voted early before Tuesday, indicating the high energy. The campaign has attracted more than $11 billion in political advertising, while billionaire Trump ally Elon Musk has poured hundreds of millions of dollars into Republican political efforts. As soon as polls close, concerns will mount over whether results will be accepted by the Republicans. Trump, who tried to overturn his 2020 election defeat, has repeatedly alleged widespread voter fraud and accused Democrats -- with no evidence -- of cheating. The Justice Department, run by a close Trump ally, has already sued to potentially block certification of Alaska's Senate race if Republican incumbent Dan Sullivan narrowly loses, although a court ruled against the effort on the eve of the election. Trump, who will watch the midterm results at the White House on Tuesday night, signalled that if he does lose control of Congress, he could simply defy Democrats. "I veto everything," he told a podcast Monday, although he said he might strike deals with Democrats eventually.